Does the tolerance of sugarcane to excess water in the soil depend on the stage of development? / A tolerância da cana-de-açúcar ao excesso de água no solo depende do estádio de desenvolvimento?

Soil waterlogging reduces the availability of oxygen to the roots of the plants, which makes necessary an efficient drainage system for correction. Thus, the objective of this study was to evaluate the tolerance of sugarcane in flooded crop with different velocities of lowering the groundwater in three stages of ratoon sugarcane development. The experiment was carried out in a randomized complete block design (3 x 5 + 1), with three developmental stages (44, 210 and 305 days after planting) and five groundwater falling velocities (30 cm in 3, 6, 9, 12 and 15 days) and the control (irrigation without flooding the soil). There was a significant effect for groundwater retraction velocities and evaluation periods for leaf area (LA) and leaf area index. The treatments P1V4 and P2V3 presented the highest LAs (0.91 m²). The first sugarcane ratoon was tolerant to soil waterlogging at different stages of development and to different groundwater falling velocities, with no major losses in plant development and productivity, however, for total recoverable sugar cane ratoon was more sensitive when the flood occurred in the regrowth stage.

First leaf of sugar cane sensitivity to soil

A expansão do cultivo da cana-de-açúcar irá promover a incorporação de novas áreas ao processo produtivo e, neste processo, áreas com problemas de drenagem possivelmente serão utilizadas. Para o bom aproveitamento destas áreas, o dimensionamento correto de sistemas de drenagem é importante. No dimensionamento racional em regime não permanente, é necessário se conhecer a velocidade mínima de rebaixamento do lençol freático a ser proporcionado pelos drenos, o que depende da sensibilidade de cada cultura. Assim, este trabalho teve como objetivos determinar o efeito de diferentes velocidades de rebaixamento do nível freático, em diferentes estádios de desenvolvimento, da primeira soca da cana-de-açúcar. O experimento foi conduzido em 64 lisímetros de lençol freático, em um delineamento experimental de blocos casualizados, arranjado em um fatorial de (3 x 5 + 1) x 4, sendo 3 estádios de desenvolvimento, 5 velocidades de rebaixamento do nível freático, mais uma testemunha que não sofreu estresse por excesso de umidade, com 4 repetições. A primeira soca da cana-de-açúcar mostrou-se resistente ao encharcamento do solo nos diferentes estádios de desenvolvimento da cultura e para as diferentes velocidades de rebaixamento do nível freático, sem maiores prejuízos no desenvolvimento da planta e perdas de produtividade, entretanto para a variável ATR (açúcar teórico recuperável) a cana-soca apresentou-se mais sensível quando a inundação ocorrera no estádio de rebrota. A condição de inundação não alterou o pH solo.The expansion of sugar cane cultivation will promote the incorporation of new areas in the process, and in this process, areas with drainage problems possibly artificial drainage maybe used. For the proper use of these areas the correct drainage design of the systems is important. For the non-permanent rational design, it is necessary to determine the minimum speed of lowering the water table to be provided by the drains, which depends on the sensitivity of each culture. This work aims to determine the effect of different speeds of lowering the water table at different stages of development of first ratoon of sugar cane. The experiment was conducted in 64 lysimeters the water table in a randomized block design, arranged in a factorial (3 x 5 + 1) x 4, with 3 stages of development, 5-speed to lower the water table and a treatment who will not suffer stress by excessive moisture. The first sugar cane re-sprout has presented endurance to the soil flooding at the different culture stages and to the different lowering water table speeds, without higher damages to the vegetable development or even farm productivity, but according to the ATR variable, the sugar cane ratoon has shown more sensitive when the flooding has happened at the re-sprouting stage. It was conclude that none of the speeds of lowering tested at the 3 stages reduced yield. The flooding conditions did not affect soil pH

RENDIMENTO E EFICIÊNCIA DO USO DA ÁGUA PELA ALFACE EM FUNÇÃO DA LÂMINA DE IRRIGAÇÃO

The purpose of this study was to evaluate the production of lettuce Lactuca sativa cv. Verônica to water levels. The experiment was conducted at Centro de Ciências Agrárias at Universidade Federal de Roraima (State of Roraima, Brazil). The experiment was carried out in a greenhouse following the completely randomized blocks design with four replications. The treatments consisted of six water levels based on fractions of the class A pan daily evapotranspiration (20%, 40%, 60%, 80%, 100% e 120%). The results of yield and fresh matter showed a linear response of the applied irrigation levels. The water use efficiency showed a decreasing linear response with respect to the irrigation levels. The maximum of yield showed 17.35 t ha-1 with 120% Class A Pan evaporation level